JP2005134907A - Optical guide system for use in system environment of back projection type display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a design of back project that is lighter, thinner and at lower cost than the traditional design of back projection and improved visual experience. <P>SOLUTION: A display device is one provided with multiple total internal reflection (TIR) optical guides 203 that expand small original optical expression from the input 201 of each optical guide to larger optical expression from the output 202 of each optical guide. It is desirable that the substantially multiple TIR optical guides should be made of optical guide material, respectively, isolated from other substantially TIR optical guides with the material that has a refractive index lower than the optical guide material concerned, and have the angular offset between input and output and the above-mentioned original optical expression and the above-mentioned output of the above-mentioned each substantially TIR optical guide should be provided with the pixel of an image and a beveled surface, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates generally to the field of display devices, and in particular to screens and associated hardware used in a rear projection display type environment.

  Current rear projection display devices typically use a wide angle projection lens, such as a mirror, that directs light received in cooperation with a series of reflective surfaces to the back of the screen. This lens-mirror projection mechanism enlarges the image received at the wide-angle projection lens. Such rear projection display mechanisms typically range from about 30 to 60 centimeters for large screen rear projection television type displays where the diagonal length of the screen is typically in the range of about 75 to 150 centimeters. With a weight in the range of about 10-50 kilograms. In many environments, such rear projection display devices can be exposed to a variety of adverse situations, including damage and breakage in the environment in use.

  Some rear-projection display devices exhibit only average or sub-average image quality in certain environments. For example, such devices can be difficult to see when viewed from a particular angle, when light changes within the system environment, or when extreme light intensity is reached in the system environment. In these types of system environments, light output and contrast are always a problem and can adversely affect the visual experience. Viewers are also familiar with improved types of displays. This improved type of display includes, but is not limited to, a plasma display or a liquid crystal display (LCD). Although these may be more appealing than conventional rear projection displays, they can result in significant costs. Some improved lenses are used in rear projection display systems to address and improve the quality of rear projections that are of interest to higher level consumers, but the basic lens / reflector design described above. Is almost unchanged, and becomes a limiting factor between the overall image quality and the thickness of the entire system.

  Specific examples of conventional devices that incorporate such a light guide to provide such attributes include US Pat. No. 4,116,739 to Glenn entitled “Method of Forming an Optical Fiber Device”, and US Pat. No. 5,381,502 to Veligdan named “Flat or Curved Thin Optical Display Panel” is included. The optical fiber device of US Pat. No. 4,116,739 can be prohibitively expensive for large screens used in the home television market. The display panel of US Pat. No. 5,381,502 has the disadvantage of an optical effect known as “keystone” unless the projection system is very far from the input surface of the panel, which is undesirable. there is a possibility. Combining a reasonably compact display panel and projection optics can result in an unacceptable image.

  Weight, thickness, durability, cost, and quality are important considerations for rear projection television displays and display screens. An advantage over the prior art would be to provide a rear projection design that is lighter, thinner and less costly than a rear projection design and provides an improved visual experience.

  According to a first aspect of the present invention, a display device is provided. The display device comprises a plurality of substantially total reflection (TIR) light guides that expand the small original optical representation at the input of each light guide to the output of a larger optical representation at the output of each light guide. .

  According to a second aspect of the present invention, a method for manufacturing a display device is provided. The method includes providing a layer of light guide material, placing a layer of lower refractive index material on the light guide material, adding an additional layer of light guide material and a lower refractive index material. Alternate layers are alternately deposited on the lightguide material, thereby forming a layered stack and forming a channel in the layered stack by cutting, thereby providing a plurality of layers. Creating a substantially total internal reflection (TIR) light guide.

  According to a third aspect of the present invention, an apparatus for providing light to a display is provided. The apparatus is oriented to expand a relatively small original optical representation from the input of each light guide to a relatively large optical representation output at the output of each light guide. A substantially total reflection (TIR) light guide is provided. The plurality of substantially total reflection light guides are each isolated from the other substantially total reflection light guides by a material having a lower refractive index than the respective substantially total reflection light guides.

  These and other objects and advantages of all aspects of the present invention will become apparent to those of ordinary skill in the art upon reading the following detailed disclosure of the preferred embodiments shown in the drawings.

  The present invention will now be described by way of example and not limitation in the accompanying drawings.

  The present invention is generally applicable to many different screen assemblies, and is particularly suitable for screen assemblies used in rear projection systems. In order to facilitate the description and understanding of the various aspects of the present invention, specific examples of such screen assemblies are provided herein, but the description to be made and the present invention itself are intended to be illustrative of such examples. It is not intended to be limited to details.

  FIG. 1 shows a conventional design of a conventional rear projection that includes a source 101. The source 101 can provide an analog or digital signal in bits, individual pixels, the entire image format, or other applicable input format. The input format may be converted by the converter 102 into the entire image. The converter 102 typically acquires a digital signal and converts it to analog, or receives a television signal and converts it to one or more images. Converter 102 is a generic representation of a device that receives an input signal in a particular format and converts such signal into an image or a continuous image. The wide-angle projection lens 103 receives the converted image, sends it to a series of reflecting surfaces 104, and sends it to the screen 105. Multiple wide-angle projection lenses, such as three or multiples of 3, may be used for the red, green, and blue aspects of the display. Note that only one of the reflective surfaces 104 is visible from the side view shown in FIG. More than one reflective surface may be used.

  The design of the present invention is directed to a screen manufactured using a series of light guides made of patterned plastic layers used to send pixels from the source or input to the display or display screen. FIG. 2 is a conceptual and theoretical representation of the design of the light guide for explaining each element of the light guide and not its specific design. Input location 201 receives pixels, image portions, or light energy at a series of points or input locations for individual light guides 203, such as individual squares labeled 1-8 and AD in FIG. . Other geometric light guides may be used, including but not limited to triangles, rectangles, and hexagons. The output location 202 may form an enlarged view of the received input image using bevel cuts. The angle of the slope is adjustable and may be less than about 10 degrees in the illustrated embodiment. Obviously, the larger the slope angle, the smaller the area that the light guide can occupy and / or display on the screen. Expansion in the direction orthogonal to the inclined surface is performed by adjusting the interval between adjacent light guides. The expansion in this arrangement is equal to the ratio of the inter-guide spacing of the output end to the input end. In some cases, the enlargement in the central region may be different from the enlargement of the peripheral region.

  The example shown in FIG. 2 schematically shows all light guides 203 with a relatively sharp 90 degree curvature, in addition to ramping the ends of the light guides for the purpose of displaying the received input signal. Show. In practice, the radius of curvature of such a bend may be in the range of at least about 10 times the width of the input side of any given light guide. Although not necessarily at the angle of about 90 degrees as shown, this design uses bending or turning of the light guide 203 to increase the size at the output location 202. FIG. 3 shows an embodiment of the design of a light guide with a more gentle curve, which also results in an angle that is 90 degrees different from the input. The length of the entire light guide 203 can be linearly extended by placing a light guide extension at the input location 201 or output location 202, or otherwise modified to provide various geometric shapes of light guides. It is clear that can be able to send optical signals from the source and input location 201 to the output location 202 and the display or display screen.

  The curvature, bend, or difference between the light guide input and output may vary depending on the media used to construct the light guide and / or cladding material, the application, if present, the slope of the light guide output, and various It may vary depending on other factors. A critical parameter is that the system and design provide a substantially total reflection or TIR light guide, described below, where the light received at each light guide input location 201 is light with minimal loss. The output location 202 is substantially transmitted.

  As can be seen, especially when each light guide represents one pixel of a high definition image, a significantly more than 12 light guides as shown in FIG. Can be realized. Hundreds, thousands, or more of light guides 203 may be used with a single display. The output location 202 may form part of the screen, or another screen may be used to prevent the output location from being exposed outside the device.

  The structure of the light guide and associated elements may vary depending on the circumstances. In the illustrated embodiment, the individual light guide core sheets are optically substantially transparent plastic or plastic type materials, including but not limited to plastics such as acrylic, plexiglass, or polycarbonate materials. May be formed. The core material of the light guide may have a low level of birefringence depending on the environment used. The material used to construct the light guide may or may not have polarity. This is because the presence or absence of polarity may benefit a particular design. An acrylic resin sheet may be provided on the substrate and stacked in layers. The substrate may be any type of substrate suitable for supporting and affixing an acrylic resin or other plastic material used as the core material. As shown in FIG. 4, the plastic or plastic type material that forms the light guide core 402 is optionally coated with an optional substrate 405 by embossing, silkscreen printing, inkjet printing, laser cutting, or other available techniques. It may be formed on top. The light guide 203 may isolate individual light guides using a material such as a clad material 401 having a refractive index lower than that of the core 402. A cross-sectional view of such individual elements is shown in FIG. The cladding material 401 may be, for example, a glue having a relatively low refractive index compared to the core 402 or some other type of bonding agent. Such adhesives or bonding agents may be formed from vulcanized bonding agents or silicone adhesives such as those available from General Electric Corporation or Dow Corning Corporation. Good. The clad material may surround all the light guide cores, such as the light guide core 402, or any layer of clad material, such as an adhesive layer, disposed between any horizontal layers of the light guide. Note that it may be distributed in other ways. For vertical isolation, another cladding material may be provided, such as air, vacuum, or other suitable material. Other clad material arrangements may be used, including but not limited to isolating individual light guides using one or more clad materials.

  An optional substrate 405 may or may not be used, as its name suggests. If an optional substrate is not used, the light guide forms a bottom horizontal layer and is formed of a core material. More than one core material may be used for the light guide 203. The light guide 203 that can be formed of a layered material may be formed by dividing each layer to form a light guide as shown in FIG. The light guides are optically isolated from each other using cladding material 401 or air. The clad material 401 allows light energy to be captured and provides total internal reflection or TIR in certain geometric shapes.

  Total internal reflection (TIR) means that all incident light is reflected at the boundary. TIR occurs only when a ray is in a denser medium and approaches a sparser medium, and the incident angle of the ray is greater than the “critical angle”. The critical angle is defined as an incident angle at which the refraction angle emitted is 90 degrees when light abuts the boundary from the denser medium side. For any angle of incidence greater than the critical angle, light transmitted through a denser medium is totally reflected. The critical angle value is determined by the combination of materials on either side of the boundary.

For each of the incident and refractive media such as the light guide material and cladding material shown in the present invention, the critical angle is the incident angle Θ _i of the incident medium such that the incident angle Θ _r of the refractive medium is 90 degrees. is there. In general, the critical angle is equal to the inverse sine function of the refractive index ratio. That is,
Θ _i = sin ⁻¹ (n _r / n _i ) (1)

Where n _r and n _i are the refractive indices of the refractive material and the incident material, respectively. Since TIR occurs only when the refractive medium is sparser than the incident medium, the value of n _i should be greater than the value of n _r . In the present invention, the refractive index of the light guide material must be greater than the refractive index of the cladding material. In the present invention, the internal scattering level is minimized both in the horizontal and vertical directions.

  The light guide is formed by providing an optional first layer or substrate, applying either a clad material or a sheet of light guide material to the optional first layer, and then the sheet of light guide material and the clad material And alternately layering on top of the previously formed layer. Affixing the light guide sheet may be performed using heat or lamination techniques. The completed layered stack then provides a series of channels that can be engraved with channels and can contain only air or additional cladding material, or any material with the appropriate refractive index, and is essential A TIR can be provided. The channel is usually not straight, but instead has a non-insubstantial angle between the input and output, possibly including an angular difference of more than 45 degrees to about 90 degrees May have. More than one bend or turn may be provided between input and output, using the described channel formation by cutting. At least one of the ends of the light guide array so formed may have an oblique cut at an angle less than about 10 degrees as described.

  In forming a layer of clad material and core material, i.e., light guide material, the clad material usually cannot dissolve the core material. If a cladding material, such as an active adhesive or bonding agent, melts the core material, the reflection of light within the light guide will be random or unpredictable and no TIR will result.

  The light guides at the input end 201 and the output end 202 are arranged to preserve the relative position between the pixels so that the square input is sent as a square output having the same or similar aspect ratio. The light guide input aspect ratio and the output aspect ratio may be different depending on the situation. For example, the image projected on the input end of the light guide is pixilated by the individual light guides and has different aspect ratios based on the different aspect ratios between the input end and the output end of the light guide. An enlarged pixelated image can be produced at the output of the ratio light guide. In particular, when the slope angle is different as in the geometrical shape shown in FIG. 2, the horizontal magnification may be different from the vertical magnification. Taking into account the difference in magnification and the slope angle, the final result, i.e. the light guide output sent to the screen, may produce an isotropic ratio image. As shown in FIG. 2, the numbers and letters shown in the light guide 203 indicate a connection and identify individual light guides, but image or pixel storage or magnification / aspect within each individual light guide. The ratio is not shown.

  When multiple layers of core material are used, each light guide may be isolated from other light guides on each layer by an air gap. Furthermore, the substrate of the light guide may be a clad material. In forming the entire light guide and the display, a plurality of sheets may be laminated to form a stacked layer. The plurality of sheets may be formed of a core material, a clad material, and a substrate, or may be alternately formed of a core material and a clad material. In one embodiment, the minimum number of layers may be equal to the number of desired pixels in one direction on the display, which is generally either vertical or horizontal. Individual light guides may be formed after several sheets of core material are laminated, for example by laser cutting through the layers of laminated material.

  An example of an embodiment of an individual light guide is shown in FIG. From FIG. 5, the width of the output 501 is larger than the input, and may be sloped for appropriate enlargement. Input 502 receives a small size image and sends it to output 501 via bend 503. The output 501 is ramped to provide a magnification of about 5 to 50 times in the illustrated orientation of the received image. Depending on circumstances such as available spacing, a linear enlargement of about 5 to 50 times may be used. Although FIG. 5 shows one 90 degree bend 503, more than one bend may be used in a single light guide, depending on the desired geometry.

  The operation of the individual light guides uses internal reflection and may vary depending on the geometry. FIG. 6 shows light rays traveling through individual light guides that are generally of minimal loss and TIR. The light exits the slope area of output 601 after being reflected many times within the slope area. Due to the slope at the output 601, the internal angle of the light beam becomes smaller than the critical angle. In conventional designs, usually only a fraction of the light reaches a person looking at the screen from a direction perpendicular to the tapered edge. In the mechanism of the present invention, a significant portion of the light energy is directed to the observer. From the design of FIG. 6, the bevel is about 5 degrees, and light exits the beveled edge at an angle less than about 25 degrees with respect to the beveled output end surface.

  FIG. 7 shows an auxiliary lens-reflector mechanism intended to change the direction of light emitted from the beveled region of output 601. The reflection device 701 receives the light reflected from the sloped end and uses a series of reflectors 701a-e. The reflectors 701a to 701e reflect the light received from the slope region or the sloped surface of the light guide output 601 toward the observer or virtual observer. The design of FIG. 7 increases the brightness of the display. Further, in some directions, when the reflection device 701 is used to eliminate reflection in the output that is the slope of the end portion of the light guide, the light travels through the light guide on the side far from the observer or virtual observer. It will not come out. Inclined reflectors 701a-e capture ambient light and increase the display contrast. Although the angles of the directions of the reflectors 701a to 701e in FIG. 7 are all the same, it is possible to provide a reflector 701 in which the angle of each reflector is changed depending on the expected incident angle of light energy received from the inclined output. Good. If the reflector is designed with various angles, the direction of the light energy can be improved with respect to the observer or the virtual observer. Further, the reflector surface may be wavy or irregular with a spacing much smaller than the size of the pixel. This wavy or irregular structure can create diffuse reflection rather than specular reflection to increase the viewing angle.

  The reflecting device may be made of the same material as the core material of the light guide with a reflecting surface formed inside, or may be made of a material whose refractive index substantially matches the core material of the light guide. The reflecting surface is made of a material that reflects substantially uniformly over the entire visible spectrum. Furthermore, although the reflecting device 701 shows a straight reflecting surface, a curved reflector such as a concave reflector is used to capture light energy better and change its direction toward an observer or a virtual observer. May be.

  Further, a further output layer such as a reflection device 701 may be attached to the output surface of the surface of the brightness enhancement layer to increase the resistance against scratches and extend the life of the screen. Such additional layers or devices may include, for example, a polycarbonate layer.

  One of ordinary skill in the art would have the benefit of having a small projection image, such as a computer display or other projection device, which may benefit from scaling up to a larger projection image with minimal loss of quality, It should be understood that the design of the present invention may be applied to other systems that display moving images. In particular, it should be understood that a variety of display and / or rear projection display designs can be accommodated by the functionality and related aspects described herein.

  For purposes of explaining how the invention can be used to advantage, an apparatus and method for projecting an image on a display using a series of light guides has been described above, but the invention is not limited thereto. It should be understood that this is not the case. Accordingly, all modifications, variations, or equivalent arrangements that may occur to those skilled in the art are to be considered within the scope of the invention as defined in the claims.

FIG. 2 illustrates a typical prior art rear projection design. FIG. 4 is a conceptual and theoretical representation of a light guide design for illustrative purposes. The actual light guide has a curvature or curvature with a radius of curvature that is at least ten times the width of the input side of the light guide. FIG. 6 shows an alternative embodiment of a light guide design that uses a gentle curvature to provide a signal that is displayed using total internal reflection (TIR). FIG. 3 is a cross-sectional view of a cladding material, a core material, and an optional substrate. It is a figure which shows the structure of each light guide. FIG. 5 shows light rays traveling through individual light guides of TIR with generally minimal loss. FIG. 5 shows an auxiliary lens-reflection mechanism intended to change the direction of light emitted from the slope region of the light guide output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101: Source 102: Converter 103: Wide angle projection lens 104: Reflecting surface 105: Screen 201: Input place 203: Light guide 202: Output place 402: Core 405: Substrate 401: Clad material 501: Output 502: Input 503: Bending 601: Output 701: Reflector 701a-e: Reflector

Claims (10)

  A display device comprising a plurality of substantially total reflection (TIR) light guides that expand a small original optical representation from the input of each light guide to an output of a larger optical representation at the output of each light guide.   Each of the plurality of substantially total reflection light guides is formed from a light guide material and is isolated from other substantially total reflection light guides by a material having a lower refractive index than the light guide material. The display device according to claim 1.   The display apparatus of claim 1, wherein the plurality of substantially total reflection light guides have an angular offset between input and output.   The display device of claim 1, wherein the original optical representation comprises image pixels.   The display device of claim 1, wherein the output of each substantially total reflection light guide comprises a beveled surface. By using a transparent material having a refractive index substantially equal to that of the light guide, the light guide includes a reflective element that is arranged close to the surface of the inclined surface and optically coupled to the inclined surface,
The reflective element comprises at least one reflector that receives light energy from the ramp and is oriented to change the orientation of the light energy to an angle that is substantially perpendicular to the ramp. A display device according to 1.   The display device according to claim 6, wherein the reflective element includes a plurality of reflectors that receive a plurality of light beams from the slope and are oriented to reflect the light beams at a predetermined angle.   The display device according to claim 7, wherein the plurality of reflectors in the reflective element prevents light from exiting the light guide from a surface that is not the inclined surface.   The display device according to claim 7, wherein the plurality of reflectors in the reflective element increase the contrast of the display device by capturing ambient light. The display device according to claim 6, wherein an output surface of the reflective element is coated with a material that enhances durability and is configured to improve visibility.

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